Pre-form ceramic matrix composite cavity and method of forming and method of forming a ceramic matrix composite component

ABSTRACT

A pre-form CMC cavity and method of forming pre-form CMC cavity for a ceramic matrix component includes providing a mandrel, applying a base ply to the mandrel, laying-up at least one CMC ply on the base ply, removing the mandrel, and densifying the base ply and the at least one CMC ply. The remaining densified base ply and at least one CMC ply form a ceramic matrix component having a desired geometry and a cavity formed therein. Also provided is a method of forming a CMC component.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

This invention was made with Government support under contract numberDE-FC26-05NT42643 awarded by the Department of Energy. The Governmenthas certain rights in the invention.

FIELD OF THE INVENTION

The present invention relates generally to gas turbines for powergeneration and more specifically to methods of forming ceramic matrixcomposite components for gas turbines.

BACKGROUND OF THE INVENTION

Silicon carbide (SiC)-based ceramic matrix composite (CMC) materialshave been proposed as materials for certain components of gas turbineengines, such as the turbine blades, vanes, nozzles, and buckets.Various methods are known for fabricating SiC-based CMC components,including Silicomp, melt infiltration (MI), chemical vapor infiltration(CVI), polymer inflation pyrolysis (PIP), and oxide/oxide processes.Though these fabrication techniques significantly differ from eachother, each involves the use of hand lay-up and tooling or dies toproduce a near-net-shape part through a process that includes theapplication of heat at various processing stages.

As with turbine blades and vanes formed from more conventionalsuperalloy materials, CMC blades and vanes are primarily equipped withcavities and cooling passages to reduce weight, reduce centrifugal load,and reduce operating temperatures of the components. These features aretypically formed in CMC components using a combination of removable andexpendable tooling.

Forming CMC component with a cavity includes a number of steps,including using pre-forms. First, a plurality of ceramic plies, some ofwhich can include reinforcing material or are pre-impregnated withmatrix, are laid up on a mandrel or mold in a pre-determined pattern toprovide desired final or near-net-shape and desired mechanicalproperties of component. The mandrel is generally selected from variouspolymers, or other meltable materials. The laid-up plies may bepre-impregnated (pre-preg) with matrix material, such as SiC orimpregnated with matrix after lay-up of the plies. Prior to rigidizationof the CMC pre-form, the mandrel is removed through a burn-out cycle. Inthe burn-out cycle, the mandrel forming materials, such as, variouspolymers, or other meltable materials are melted out.

After the burn-out cycle, the CMC pre-form component is very fragile dueto burn-off of the volatile substances of the composite. In certaincases, one end of the CMC pre-form requires capping or closing beforeuse in gas turbines in order to close off the hollow region for use inthe turbine. In known processes, to close the open end area of the CMCpre-form a cap or plug is inserted after the burnout cycle when the CMCpre-forms are in their most fragile state. The plug can be formed fromof a CMC laminate part having a number of plies, and shaped so as tofill the open end of the CMC pre-form. Use of a separate forming,cutting and layup process is time and labor intensive simply to create aclosed structure. Challenges also arise with placing the pre-rigidizedCMC laminate having a number of plies into the open end. For example,because both the CMC laminate and pre-form are fragile prior todensification, these components can be easily damaged during assembly.

Therefore, a method of forming pre-form ceramic matrix composite cavity,a pre-form ceramic matrix composite cavity, and a method of formingceramic matrix composite components that do not suffer from the abovedrawbacks is desirable in the art.

SUMMARY OF THE INVENTION

Certain embodiments commensurate in scope with the originally claimedinvention are summarized below. These embodiments are not intended tolimit the scope of the claimed invention, but rather these embodimentsare intended only to provide a brief summary of possible forms of theinvention. Indeed, the invention may encompass a variety of forms thatmay be similar to or different from the embodiments set forth below.

According to an exemplary embodiment of the present disclosure, a methodof forming pre-form ceramic matrix composite cavity for a ceramic matrixcomponent is provided. The method includes providing a mandrel andapplying a base ply to the mandrel. The method includes laying-up atleast one CMC ply on the base ply, removing the mandrel and densifyingthe base ply and the at least one CMC ply. The remaining densified baseply and at least one CMC ply form a ceramic matrix component having adesired geometry and a cavity formed therein.

According to another exemplary embodiment of the present disclosure, apre-form ceramic matrix composite cavity for a ceramic matrix compositecomponent is provided. The pre-form ceramic matrix composite cavityincludes a cavity conforming to a mandrel geometry. The pre-form ceramicmatrix composite cavity includes a densified base ply defining thecavity. The pre-form ceramic matrix composite cavity includes at leastone densified lay-up ply applied to the densified base ply. The pre-formceramic matrix composite having a desired geometry and the cavity formedtherein.

According to another exemplary embodiment of the present disclosure, amethod of forming a ceramic matrix composite component is provided. Themethod includes providing a lay-up tool having a first surface and asecond surface. The method includes applying a first base ply to thefirst surface of the lay-up tool. The method includes laying-up a firstset of CMC plies adjacent to the first base ply. The method includesproviding a pre-form ceramic matrix composite cavity. The pre-formceramic matrix composite includes a cavity conforming to a mandrelgeometry, a densified base ply defining the cavity, and at least onedensified lay-up ply applied to the densified base ply, the pre-formceramic matrix composite cavity having a desired geometry and the cavityformed therein. The method includes placing the pre-form ceramic matrixcomposite cavity adjacent to the first set of CMC plies in the lay-uptool. The method includes laying-up a second set of CMC plies adjacentto the pre-form ceramic matrix composite cavity. The method includesapplying a second base ply to the second set of CMC plies, the secondbase ply adjacent to the second surface of the lay-up tool. The methodincludes densifying the first base ply, the first set of CMC plies, thepre-form matrix ceramic composite cavity, the second set of CMC plies,and the second base ply. The ceramic matrix composite is formed having adesired geometry and the cavity formed therein.

Other features and advantages of the present invention will be apparentfrom the following more detailed description of the preferredembodiment, taken in conjunction with the accompanying drawings whichillustrate, by way of example, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a ceramic matrix composite (CMC)component of the present disclosure.

FIG. 2 is a perspective view of pre-form CMC cavity of the presentdisclosure.

FIG. 3 is a sectional view taken in direction 3-3 of FIG. 2 of thepre-form CMC cavity of the present disclosure.

FIG. 4 is a schematic view of FIG. 3 after a mandrel is removed anddepicting the pre-form CMC cavity of the present disclosure.

FIG. 5 is a schematic view of FIG. 4 including air foil shell plies ofthe present disclosure.

FIG. 6 is a perspective view of the lay-up tool of the presentdisclosure.

FIG. 7 is schematic view of the layers for the CMC component in thelay-up tool of the present disclosure.

FIG. 8 is sectional schematic view of CMC component of the presentdisclosure.

FIG. 9 is a flow chart of the method of making the pre-from ceramicmatrix composite of the present disclosure.

FIG. 10 is a flow chart of the method of making a CMC component of thepresent disclosure.

Wherever possible, the same reference numbers will be used throughoutthe drawings to represent the same parts.

DETAILED DESCRIPTION OF THE INVENTION

Provided is an economically viable method of forming a ceramic matrixcomposite (CMC) component, specifically a method of forming a CMC bladeor vane, in such a manner that, the CMC components do not suffer fromthe processing and performance drawbacks in the prior art. One advantageof an embodiment of the present disclosure includes an opening in thebottom cavity to allow for melt-out of the mandrel material and cleaningof the cavity. Yet another advantage is a tip cap and cavity combinationthat is highly durable because it has undergone densification. Anotheradvantage of an embodiment of the present disclosure includes a reducedply volume of the blade shell at the time of melt-out of the mandrelmaterial which allows for better control of the melt-out of the mandrelmaterial. Yet another advantage of the present embodiment is that aformed pre-form CMC cavity for forming a CMC component allows for cavityinspections prior to lay-up of the air foil plies, which prevents theloss of the whole component if cavity defects are found. Anotheradvantage is that the tip cap portion of the pre-form ceramic matrixcomposite cavity can be used for location of the pre-form ceramic matrixcomposite cavity in the lay-up tool. Yet another advantage is that themethod allows for better process control during the autoclave cycle inlay-up tool which enables better dimensional control. Another advantageis that the method allows for using tailored polymers or other mandrelmaterials for the mandrel that will melt-out or leach out duringsubsequent processing.

One or more specific embodiments of the present invention will bedescribed below. In an effort to provide a concise description of theseembodiments, all features of an actual implementation may not bedescribed in the specification. It should be appreciated that in thedevelopment of any such actual implementation, as in any engineering ordesign project, numerous implementation-specific decisions must be madeto achieve the developers' specific goals, such as compliance withsystem-related and business-related constraints, which may vary from oneimplementation to another. Moreover, it should be appreciated that sucha development effort might be complex and time consuming, but wouldnevertheless be a routine undertaking of design, fabrication, andmanufacture for those of ordinary skill having the benefit of thisdisclosure.

When introducing elements of various embodiments of the presentinvention, the articles “a,” “an,” “the,” and “said” are intended tomean that there are one or more of the elements. The terms “comprising,”“including,” and “having” are intended to be inclusive and mean thatthere may be additional elements other than the listed elements.

Systems used to generate power include, but are not limited to, gasturbines, steam turbines, and other turbine assemblies such as landbased aero-derivatives used for power generation. In certainapplications, the power generation systems, including the turbomachinerytherein (e.g., turbines, compressors, and pumps) and other machinery mayinclude components that are exposed to heavy wear conditions. Forexample, certain power generation system components, such as blades,buckets, casings, rotor wheels, shafts, shrouds, nozzles, and so forth,may operate in high heat and high revolution environments. Thesecomponents are manufactured using ceramic matrix composites and thesecomponents may also include cooling passages. The present disclosureprovides method to form ceramic matrix composite (CMC) componentsincluding cooling passages. An exemplary embodiment of the disclosure isshown in FIGS. 1-8 as a turbine blade, but the present disclosure is notlimited to the illustrated structure.

FIG. 1 is a perspective view of a CMC component 10, such as but notlimited to a turbine blade 20 or turbine vane. Turbine blade 20 ispreferably formed of a ceramic matrix composite (CMC) material. Materialfor CMC component 10 includes, but is not limited to, an oxide basedCMCs such as, but not limited to alumina, mullite, boron nitride, boroncarbide, sialons (silicon, aluminum, oxygen, and nitrogen),intermetallics, and combinations thereof A suitable example of materialfor CMC component 10 is, but not limited to, AN-720 (oxide-oxide based),which is available from COI Ceramics, Inc., San Diego, Calif., or ahybrid oxide CMC material. Suitable examples of materials used to makeCMC components 10, include but are not limited to, SiC fibersimpregnated with a SiC and carbon matrix with various binders. Turbineblade 20 includes an airfoil 22 against which the flow of hot exhaustgas is directed. Turbine blade 20 is mounted to a turbine disk (notshown) by a dovetail 24 which extends downwardly from airfoil 22 andengages a slot on the turbine disk. A platform 26 extends laterallyoutwardly from the area where airfoil 22 is joined to dovetail 24.Turbine blade 20 includes at least one cavity 120 as shown in FIG. 2,extending along the interior of airfoil 22. During operation of powergeneration system, a flow of cooling air is directed through cavity 120to reduce the temperature of airfoil 22.

CMC turbine blade 20, as shown in FIG. 1, is constructed using a lay-uptechnique and a near-net shape pre-form CMC cavity 100 (see FIGS. 2-5).Turbine blade 20 also includes blade tip 30. As shown in FIG. 2,pre-form CMC cavity 100 includes a cavity 120 and a tip member 130inserted into blade tip 30. Tip member 130 is formed from a plurality ofplies 132 constructed separately in a tool or mold. Plies 132 areselected from ceramic plies that can include reinforcing material or arepre-impregnated with a matrix (see FIG. 3). An example of material forplies 132 includes, but is not limited to carbon, binder material andcoated SiC fibers. As shown in FIG. 3, mandrel 110 is used to formpre-form CMC cavity 100. In forming pre-form CMC cavity 100, at leastone base ply 112 is applied to mandrel 110. In an alternativeembodiment, more than one base plies 112 are applied to the mandrel. Anexample of suitable material for base ply 112, includes but is notlimited to, plies containing carbon, SiC and binders. Next, at least oneceramic matrix composite (CMC) ply 114 is applied to the at least onebase ply 112. An example of material for CMC 114 includes but is notlimited to carbon, binder materials and coated SiC fiber. After at leastone base ply 112 and at least one CMC ply 114 are assembled in desiredgeometry or shape on mandrel 110, the mandrel 110 is removed. Mandrel110 material is any material that can be removed from the densifiedstructure by melting or chemical removal methods. Suitable examples ofmandrel material include, but are not limited to, polymers, or othermeltable or leachable materials. After the mandrel 110 is removed, atleast one base ply 112 and at least one CMC ply 114 are densified.Densification includes, but is not limited to melt infiltration,chemical vapor deposition, or other suitable densification methods.After densification, densified base ply 112 and at least one CMC ply 114form pre-form CMC cavity 100 having a desired geometry and a cavity 120formed therein, as shown in FIG. 4.

In one embodiment, base ply 112 is applied to mandrel 110 but adjacentto tip member 130. Next, at least one ceramic matrix composite (CMC) ply114 is applied to the at least one base ply 112 on mandrel 110 and tipmember 130, as shown in FIG. 3. After at least one base ply 112 and atleast one CMC ply 114 are assembled in desired geometry or shape onmandrel 110, the assembly is autoclave processed and then mandrel 110 isremoved, by methods, such as, but not limited to, melt-out or leachingprocesses depending on the mandrel composition. After removal of mandrel110, at least one base ply 112, at least one CMC ply 114, and tip member130 are densified. Densification includes, but is not limited to, meltinfiltration, chemical vapor deposition, or other suitable densificationmethods. Densified base ply 112, at least one CMC ply 114, and tipmember 130 form pre-form CMC cavity 100 having a desired geometry and acavity 120 formed therein, as shown in FIGS. 3-4.

As shown in FIG. 4, mandrel 110 is removed and cavity 120 is formed bymandrel geometry 111 that remains after melt-out of mandrel 110. Also asshown in FIG. 4, in one embodiment, a portion 134 of tip member 130 isremoved by machining to create location feature 136 for lay-up tool 200(see FIG. 6). In another embodiment, no machining is necessary to createlocation feature 136 for lay-up tool 200.

As shown in FIGS. 5-7, pre-form CMC cavity 100 is used in lay-up tool200 (see FIG. 6) to form CMC component 10 (see FIG. 8). As shown in FIG.6, lay-up tool 200 can be used for fabricating or pre-forming CMCcomponent 10 including pressure side 12 and suction side 14, dovetail24, and platform 26. Generally, lay-up tool 200 includes a first set ofopposing sides 202, 204 configured to abut each other and be fastenedtogether. As shown in FIG. 6, sides 202, 204 can be arranged as a moldfor CMC component 10. Sides 202, 204 can include a first lay-up surface206 designed to permit fabrication of the desired shape for CMCcomponent 10. Tool 200 further includes a second set of opposing sides208 configured to provide pressure on airfoil and dovetail 24,respectively (or, in the alternate embodiments, on the blade surrogate).Tool 200 may include a dovetail die 212 and/or a bridge 214 or otherstructures to provide a selectively configurable surface for laying uppreform material, such base ply 112 and CMC plies 114. In oneembodiment, the dovetail die 212 may further define a lay-up surface,for example the first lay-up surface. In another embodiment, thedovetail die 212 is configured for the airfoil and dovetail preform andthe integral platform preform to be co-densified.

As shown in FIG. 7, in forming component 10, a first baseply 600 isapplied to first surface 206 of lay-up tool 200. Next, first set of CMCplies 602 are applied adjacent to first baseply 600. Next, pre-form CMCcavity 100 is applied adjacent to first set of CMC plies 602. Next, asecond set of CMC plies 604 is applied adjacent to pre-form CMC cavity100. A second baseply 606 is applied adjacent to second set of CMC plies604 and adjacent to second surface 207 of lay-up tool 200. After all ofthe items are situated in lay-up tool 200, first baseply 600, first setof CMC plies 602, pre-form CMC cavity 100, second set of CMC plies 604,and second baseply 606 an autoclave cycle is completed. The lay-up toolincluding first baseply 600, first set of CMC plies 602, pre-form CMCcavity 100, second set of CMC plies 604, and second baseply 606 issubject to typical autoclave pressures and temperature cycles used inthe industry for composite materials. Autoclaving pulls out anyvolatiles in remaining in the plies and autoclave conditions can bevaried depending on the ply material. After autoclaving a pre-formcomponent having the desired geometry is available. The pre-formcomponent is removed from the tooling and undergoes a burn-out processto remove any remaining mandrel material or additional binders in thepre-form component. The burn-out process is generally conducted at atemperature of approximately 426-648° C. (approximately 800-1200° F.).After burn-out, the pre-form component is placed in a vacuum furnace fordensification. Densification can be conducted in a vacuum furnace havingan established atmosphere at temperature above 1200° C. to allow siliconor other materials to melt-infiltrate into the pre-form component.During densification the pre-form component, having a geometry like thatof the component 10 and including first baseply 600, first set of CMCplies 602, pre-form CMC cavity 100, second set of CMC plies 604, andsecond baseply 606 is melt-infiltrated with Silicon or other materialsto provide rigidity to CMC component 10.

A method 900 of forming a pre-form CMC cavity 100 is shown in FIG. 9.Method 900 includes providing lay-up tool, step 901. Method 900 includesproviding mandrel 110 (see FIG. 3), step 903. Method include applyingbase ply 112 to mandrel 110 and optionally applying base ply 112 to tipmember 130 (if present) (see FIG. 3), step 905. Method 900 includeslaying-up at least one CMC ply 114 adjacent to base ply 112 on mandrel110 in a lay-up tool(see FIG. 3), step 907. Method 900 includes removingmandrel 110 (see FIG. 4), step 909. After mandrel 110 is removed, baseply 112, and at least one CMC ply 114, are densified, step 911. Method900 includes removing mandrel 110 using any suitable method, such as butnot limited to melting or leaching. After the step of densifying, step911, a pre-from CMC cavity 100 remains having cavity 120 conforming tomandrel geometry 111, as shown in FIG. 4.

A method 1000 of forming a CMC component 10 is shown in FIG. 10. Method1000 includes providing lay-up tool 200 (see FIG. 6), step 1001. Method1000 includes applying first baseply 600 to first surface 206 of lay-uptool 200 (see FIG. 7), step 1003. Method 1000 includes laying up firstset of CMC plies 602 adjacent to first baseply 600 on first surface 206of lay-up tool (see FIG. 7), step 1005. Method 1000 includes providingpre-form CMC cavity 100 (see FIG. 5), step 1007. Pre-form CMC cavity 100includes cavity 120 conforming to mandrel geometry 111, densified baseply 112 defining cavity 120 and at least one densified lay-up plyapplied to densified base ply 112 (see FIG. 4). Method 1000 includesplacing pre-form CMC cavity 100 adjacent to first set of CMC plies 602in lay-up tool 200 (see FIG. 7), step 1009. Method 1000 includeslaying-up a second set of CMC plies 604 adjacent to pre-form CMC cavity100 in lay-up tool 200 (see FIG. 7), step 1011. Method 1000 includesapplying second baseply 606 to second set of CMC plies 604, secondbaseply 606 being adjacent to second surface 207 of lay-up tool 200 (seeFIG. 7), step 1013. Method 1000 includes densifying first baseply 600,first set of CMC plies 602, pre-from CMC cavity 100, second set of CMCplies 604, and second baseply 606 (see FIG. 7), to form CMC component10, step 1015. Prior to the step of densifying, step 1015, all of theitems are situated in lay-up tool 200, first baseply 600, first set ofCMC plies 602, pre-form CMC cavity 100, second set of CMC plies 604, andsecond baseply 606 are autoclaved. After autoclaving a pre-formcomponent having the desired geometry is removed from the lay-up tool200 and undergoes a burn-out cycle. After burn-out, the pre-formcomponent is placed in a vacuum furnace for densification. Afterdensification formed CMC component 10 (see FIG. 1), includes a cavity120 formed therein (see FIG. 8). After formation, component 10 can bemachined to remove additional material from tip member 130 to form tipcap 138 (see FIG. 8).

While the invention has been described with reference to a preferredembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

What is claimed is:
 1. A method of forming pre-form ceramic matrixcomposite (CMC) cavity for a ceramic matrix component comprising stepsof: providing a mandrel; applying a base ply to the mandrel; laying-upat least one CMC ply on the base ply; removing the mandrel; densifyingthe base ply and the at least one CMC ply; and wherein the densifiedbase ply and at least one CMC ply form the pre form ceramic matrixcomponent cavity having a desired geometry and a cavity formed therein,the cavity extending along an interior space in the component andwherein the cavity remains when the pre-form CMC cavity is subjected tosubsequent laying up of additional CMC plies, autoclaving anddensification.
 2. The method of claim 1, including an additional stepprior to the step of applying the base ply to the mandrel of aligning atip member adjacent to the mandrel.
 3. The method of claim 2, includingan additional step after removing the mandrel of machining the tipmember to remove additional material.
 4. The method of claim 1,including an additional step after removing the mandrel of laying-up afirst set of CMC plies in a lay-up tool and applying the pre-formceramic matrix composite cavity to the first set of CMC plies in thelay-up tool.
 5. The method of claim 4, including an additional stepafter the step of applying the pre-form ceramic matrix composite cavityof laying-up a second set of CMC plies to the pre-form ceramic matrixcomposite cavity.
 6. The method of claim 5, including an additional stepafter laying-up the second set of CMC plies of processing the first setof CMC plies, the pre-form ceramic matrix composite cavity, and thesecond set of CMC plies in the lay-up tool to form the ceramic matrixcomposite component.
 7. The method of claim 1, wherein the step ofdensifying includes melt infiltration or chemical vapor deposition. 8.The method of claim 1, wherein the step of removing the mandrel includesheat or chemical removal methods.
 9. A method of forming a ceramicmatrix composite (CMC) component comprising steps of: providing a lay-uptool having a first surface and a second surface; applying a first baseply to the first surface of the lay-up tool; laying-up a first set ofCMC plies adjacent to the first base ply; providing a pre-form ceramicmatrix composite cavity comprising: a cavity conforming to a mandrelgeometry; a densified base ply defining the cavity; and at least onedensified lay-up ply applied to the densified base ply, the pre-formceramic matrix composite cavity having a desired geometry and the cavityformed therein, the cavity forming an interior space in the component;placing the pre-form ceramic matrix composite cavity adjacent to thefirst set of CMC plies in the lay-up tool; laying-up a second set of CMCplies adjacent to the pre-form ceramic matrix composite cavity; applyinga second base ply to the second set of CMC plies, the second base plyadjacent to the second surface of the lay-up tool; after the step ofapplying the second base ply, autoclaving the first base ply, the firstset of CMC plies, the pre-form ceramic matrix composite cavity, thesecond set of CMC plies, and the second base ply; and densifying thefirst base ply, the first set of CMC plies, the pre-form ceramic matrixcomposite cavity, the second set of CMC plies, and the second base ply;wherein the ceramic matrix composite is formed having a desired geometryand the cavity formed therein.
 10. The method of claim 9, wherein theceramic matrix composite cavity includes a tip member.
 11. The method ofclaim 9, including an additional step of after the step of densifying ofinserting a tip member into the pre-from ceramic matrix compositecavity.
 12. The method of claim 9, including an additional step afterthe step of densifying of machining the ceramic matrix composite to adesired geometry.
 13. The method of claim 9, wherein the step ofdensifying includes melt infiltration or chemical vapor deposition. 14.The method of claim 9, including an additional step of after the step ofautoclaving of removing the tool.
 15. The method of claim 14, includingan additional step after the step of removing the tool of burn-out ofthe first base ply, the first set of CMC plies, the pre-form ceramicmatrix composite cavity, the second set of CMC plies, and the secondbase ply.